The instant invention relates to a method of selectively providing a metal on a surface of a substrate, in which the surface is brought into contact with a solution of a salt of that metal and said surface is locally irradiated by means of a laser beam.
Such a method is described in PCT Patent Application WO 82/03801. In the application a description is given of the provision of a metal track of, for example, platinum on a semiconductor surface of a III-V compound such as, for example, InP. For this purpose, such a surface is brought into contact with an aqueous or alcoholic solution of a platinum salt, for example H.sub.2 PtCl.sub.6. A laser beam is focussed onto the InP surface, and the semiconductor surface is displaced relative to the laser beam. At the location where the laser impinges on the semiconductor surface a chemical reaction takes place between the semiconductor surface and the solution, such that platinum is deposited on the semiconductor surface in the form of a metal. According to the present recognitions, this mechanism is based on the generation of electron-hole pairs at the semiconductor surface by irradiation by means of the laser, provided that the energy of the photons is at least equal to the gap of the semiconductor. The electrons generated reduce the metal ions to metal. In this manner a metal track having a width of 2 mm is provided selectively and without mask on a semiconductor surface. Such a method can be used for the manufacture of, for example, contact areas on Integrated Circuits (ICs).
A disadvantage of the known method is that it can only be used to plate semiconductor surfaces. The said method cannot be used to plate metal surfaces or surfaces of insulators.